Free standing mother-daughter printed circuit board contact arrangement

ABSTRACT

A free standing all metal contact which, when mounted on a first board with other similar contacts, all in a straight line, will mechanically receive and hold, and make electrical contact with a second circuit board. Each contact has U-shaped configuration with the first and second legs of the U having a width which is normal to the plane of the U. In one form of the invention the edges of both the first and second legs, or just the second leg are bent back in a direction away from the other leg to form an I beam type cross-sectional configuration to provide structural strength. Two diagonally positioned edges of the two legs are extended beyond the closed end of the U to form a pair of posts which fit into mating holes in the first circuit board to securely mount the contact thereon. The free end of the first of the two legs is bent downwardly into the U and towards the other leg to provide a spring-like gripping effect upon the edge of the second board when it is inserted into said U.

United States Patent Williams et a1.

Sept. 2, 1975 FREE STANDING MOTHER-DAUGHTER PRINTED CIRCUIT BOARD CONTACT ARRANGEMENT Inventors: Benjamin Charles Williams,

Harrisburg; Paul Robert Krider, Camp Hill, both of Pa.

Assignee: AMP Incorporated, Harrisburgh, Pa.

Filed: Apr. 5, 1974 Appl. No.: 458,385

Related US. Application Data Continuation-impart of Ser. No. 429,452, Dec. 28,

US. Cl.... 339/17 C; 339/17 LM; 339/176 MP;

339/276 SF Int. Cl. HOSK 1/07 Field of Search 339/17 C, 17 L, 17 LC,

339/17 LM, 75 MP, 176 MP, 176 ML, 276 SF [56] References Cited UNITED STATES PATENTS 2,947,964 8/1960 .lohanson ct a1. 339/17 LM 3,524,161 8/1970 Frantz et a1. 339/17'L X Primary ExaminerRoy Lake Assistant E.\'aminerE. F. Desmond Attorney, Agent, or F irm-William J. Keating, Esq.; Donald W. Phillion, Esq.

[5 7] ABSTRACT A free standing all metal contact which, when mounted on a first board with other similar contacts, all in a straight line, will mechanically receive and hold, and make electrical contact with a second circuit board. Each contact has U-shaped configuration with the first and second legs of the U having a width which is normal to the plane of the U. In one form of the invention the edges of both the first and second legs, or just the second leg are bent back in a direction away from the other leg to form an 1 beam type crosssectional configuration to provide structural strength. Two diagonally positioned edges of the two legs are extended beyond the closed end of the U to form a pair of posts which fit into mating holes in the first circuit board to securely mount the contact thereon. The free end of the first of the two legs is bent downwardly into the U and towards the other leg to provide a spring-like gripping effect upon the edge of the second board when it is inserted into said U.

7 Claims, 3 Drawing Figures PATENTEUSEP ms SHEET 1 of 2 FREE STANDING MOTHER-DAUGHTER PRINTED CIRCUIT BOARD CONTACT ARRANGEMENT CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 429,452 filed Dec. 28, 1973, by Benjamin BACKGROUND OF THE INVENTION This invention relates generally to electrical connectors for connecting a first printed circuit board, commonly known as the daughter board, to a second printed circuit board, commonly known as the mother board, and more specifically the invention relates to a simplified, all metal board-to-board connector arrangement which requires no plastic housing and which is easily installed by hand with the aid of a carrier strip which is inherently provided in the manufacture of the connector.

There are many different types of connectors in use today which are constructed to connect a first circuit board to a second circuit board. Depending upon various parameters, such as the particular type circuit boards involved, the particular environment in which the circuit boards must function. and upon individual specifications of the customer, such board-to-board connectors have widely varying characteristics and design features. For example, some board-to-board connectors are comprised of two separate plastic housings, one of which has a first set of contacts which fit into a first board and the other of which has a second set of contacts which fit into a second board. The two housings each have second sets of contacts which mate together so that the two boards are in fact connected together through the two piece connector.

Other board-to-board connectors employ a single plastic housing into which a row of connectors are embedded during the molding of the housing. Such contacts within the housing usually have a male portion and a female portion, with the male portion constructed to fit into one circuit board and the female portion constructed to receive the edge of a second circuit board.

In other type board-to-board connectors the connectors are first secured within one of the boards and then a plastic housing is snapped over the connectors in order to provide protection and support for the connectors and also to form a slot into which the edge of a second circuit board can be inserted to make contact with the contacts secured within the first board.

There are many applications for boar'd-to-board eonnectors in which no plastic housing whatever is needed, and in which the installation of the connectors can be made easily and inexpensively without the aid of expensive application tooling, and yet which have sufficient mechanical strength to effectively hold a mother and a daughter board together.

BRIEF STATEMENT OF THE INVENTION It is a primary object of the present invention to provide a board-to-board connector requiring no plastic housing.

It is a second purpose of the invention to provide a simple and inexpensive board-to-board connector which can be easily installed in a circuit board without the aid. of expensive applicator tooling andwhich re quires no plastic housing.

A third purpose of the invention is an inexpensive and reliable all metal connector," the individual contacts of which are held together by a common carrier strip to facilitate quick manual installation into a circuit board. 4 i

A fourth purpose of the invention is an all metal connector comprised of a plurality of individual contacts which can be easily installed in a circuit board'by means of a removable carrier strip and in which each' of said connectors, is constructed to mechanically grip the edge of a second circuit board to mechanically hold the two boards together as well as to provide good electrical connection between the two circuit boards.

In accordance with the invention there is provided 'a plurality of generally U-shaped contacts with the end of one leg of the U being attached to a carrier strip and with the free end of the other leg of the U being bent inwardly and downwardly toward said first leg of the U so that the row of contacts provide a slot-like arrangement formed by the inner side of thefirst leg and the bent over portion of the second leg of each of the individual contacts.

To give structural strength to the contact, both edges of each leg of the U-shaped contact are bent back about along a line parallel to the longitudinal axis' of the leg and away from the opposing leg so as to provide in each leg a cross-sectional area having a configuration something in the nature of an I-beam.

On both legs of the U one of the bent-back portions along the edge of the leg extend beyond the closed end of the U to form two posts which are inserted in holes prepared therefor in the printed circuit board. Such extensions of the bent-back portions of the legs of the U not only provide a means of mechanically mounting the contact upon a printed circuit board but also provide means for making electrical contact with both sides of the printed circuit board. Both the mechanical securing of the contacts to the board as well as the electrical contact made with the board is redundant in that two of such extensions of the legs of the U extend through holes in the board and can be soldered therein by appropriate soldering means, as for example, wave solder- In another form of the invention the said other leg of the U, having the bent inwardly and downwardly portion, does not have the edges thereof, i.e., either the main leg itself or the bent inwardly portion, bent backwards to provide additional structural strength. On the other hand, this said other leg is a flat piece of spring material metalhaving a bent-over portion which extends inwardly and downwardly into the U and with the tip thereof being bent backwardly towards the rriain portion of said other leg. The portion bent inwardly and downwardly makes contactwith the edge of a printed circuit board inserted therein. The tip extension on the bent inwardly portion functions as an anti-overstress element in that it will come into contact with the main portion of said other leg before the coefficient of elas ticity of the entire leg element has been exceeded;

The last-mentioned embodiment of the invention provides a more evenly distributed load along the entire leg, including the upright portion and the portion that is bent inwardly and downwardly into the U portion of the contact. In this manner no single portion of the leg receives an excessive amount of bending moment when the edge of the printed circuit board is inserted therein.

BRIEF STATEMENT OF THE FIGURES The above-mentioned and other features of the invention will be more fully understood from the following detailed description thereof when read in conjunction with the drawings in which:

FIG. I is a perspective view of the invention showing two of such contacts installed in a printed circuit board with the carrier strip still attached thereto;

FIG. 2 is a plan view of a printed circuit board showing the: locations of the holes in said printed circuit board for receiving the two legs of each of the U- shaped contacts of FIG. 1; and

FIG. 3 is a perspective view ofa form of the invention wherein that particular leg having a portion thereof bent inwardly and downwardly into the U does not have the edges thereof bent backwards to provide additional structural strength, but rather is essentially a flat piece of spring material metal wherein the load stress capability is distributed over the entire leg element.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, the three U-shaped contacts 10, 11 and 53 are shown mounted upon a circuit board 29. The carrier strip 15, which holds the three contacts l0, l1 and 53 together in a predetermined spatial relatiohship, is also shown in FIG. 1. It is understood that the carrier 15 is usually broken off at the score lines 40 and 41 after the contacts 10, 11 and 53 are mounted upon the board 29.

his also to be understood that while only three such contacts 10, 11 and 53 are shown mounted in circuit board 29, many such contacts can, in fact, be simultaneously mounted on the circuit board. Specifically, the receiving circuit board is prepared to receive a given number of contacts by drilling holes therein, such as the holes 31 and 30, shown in FIG. 2, for each contact. Then a portion of the carrier strip 15 is cut so as to contain the desired number of contacts, which are then mounted in the printed circuit board with the aid of the still attached carrier strip 15.

Each of the contacts, such as contacts 10, 11 and 53 are the same. Accordingly, only contact will be described in detail.

Contact 10 can be seen to be generally U-shaped in nature with two main legs 12 and 13, and a transverse connecting portion 18 connecting said two main legs together at the closed end of the'U.

One of the two legs 12 has a portion 14 which is connected to carrier strip 15 through a scored section 41 which, as mentioned above, is utilized later to break off the carrier strip 15 from the contacts.

The other leg 13 of the U-shaped contact has its free end 26 bent over and towards the other leg 12. The

bent over portion 26 is terminated at tip 24 by being bent back slightly toward the leg 13 so as to permit easy entry and withdrawal of a second circuit board (not shown) into and from between said bent-over portion 26 and the inner surface of the other leg 12.

To provide structural strength, each of the two legs 12 and 13 have their longitudinal edges bent in a direction away from each other. More specifically the leg 13 has its longitudinal edges 22 and 23 bent backwards away from the leg 12 in such a manner that bent edges 22 and 23 form a flange type feature to provide the leg 13 with the cross-sectional area somewhat similar to that of an I beam, thereby providing structural strength to the leg 13.

Similarly, the leg 12 has its two longitudinal edges 20 and 21 bent backwards away from the other leg 13 to provide a similar I-beam type structure.

The bent-over tip portion 26 of leg 13 also has its edges 25 bent over substantially at right angles to the main outer surface 45 of the bent-over portion 26 to add structural strength thereto. Because of the bentover portion 26, the edges 23 and 22 of leg 13 could be bent forward rather than backwards.

One of the flanged edges 23 of leg 13 extends downwardly beyond the closed end of the U to form a postlike element 27 which extends through a hole 31 in circuit board 29.

Similarly, one of the flange portions 20 of the other leg 12 of contact 10 extends down below the closed end 18 of contact 10 to form a post-like element 28 which extends through a second hole 30 in circuit board 29. It is to be noted that apertures 30 and 31 are positioned at diagonal corners of contact 10 to provide for the greatest mounting stability and the greatest strength of contact 10 on the surface of the circuit board 29.

Each of the two post-like elements 27 and 28 can be soldered to one or both sides of the circuit board 29. For example, leg 28 is being shown as being soldered to a metallic circuit pad 48 on the upper side of printed circuit board 29, and to a circuit pad 34 on the lower side of printed circuit board 29. Also, if desired, the leg 28 (or the leg 27) can be extended through and beyond the board 29 to form a post 54 to which an additional connection, such as a wire wrap, can be made.

The closed portion 18 of the U-shaped contact 10 is arched upwardly in the middle, i.e., portion 18 is concave with respect to the upper surface of circuit board 29 to prevent rocking of contact 10 thereon.

It is also to be noted that the three contacts l1, l0 and 53 as well as other contacts which might be connected to the carrier strip 15, can be arranged in a straight line so that a second printed circuit board (not shown) can be inserted into the gaps between the two legs of the contact. More specifically, the edge of the second circuit board is inserted between the inner surface of leg 12 of contact 10 and the inner surface 45 of the bent-over portion 26 of the other leg 13 of contact 10. It is apparent that a plurality of such contacts arranged in a row form, what is, in effect, a slot into which the edge of the second printed circuit board is inserted. Appropriate contacts, usually plated on circuit paths, are provided on the second printed circuit board to electrically mate with the individual contacts such as contacts l0, l1 and 53.

The plan view of a portion of the circuit board 29, as shown in FIG. 2, is provided only to show with more clarity the location of the holes provided therein to receive the individual contacts. More specifically, the holes 31 and 30 of FIG. 2 receive the two legs of contact 10 of FIG. 1, and holes 50 and 51 receive the two legs of contact 11.

Referring again to the bent-over portions of one of the legs of the U-shaped contacts, such as bent-over portion 26 of contact 10, it is to be noted that such bent-over portion 26 provides a spring-like force effect on the edge of a circuit board inserted therein. Such spring-like force effect will maintain a constant pressure against the contacts on the edge of the printed circuit board, and also will function to provide an antistress feature in that if the second printed circuitboard (not shown) is accidentally moved front its normal right angle position to the mother board 29, the .element 26 will give somewhat, within its elastic limits, to prevent damage being done either to the contacts. such as contacts 10, 11 or 53., or to the printed circuit contact pads on the daughter board (not shown).

Referring now to FIG. 3 there is shown another form of the invention wherein one of the legs of each of the contacts is not structurally reinforced by having the edge portions thereof bent back.

More specifically, in FIG. 3 there'are shown three contacts 100, 101 and 102 mounted on a circuit board 114, in much the same manner as the three contacts shown in FIG. 1. The contacts are carried on a common carrier strip 103 which has sprocket engaging apertures 104 and 10S therein, and in which carrier 103 can be broken off from said contacts l102 along a scored line such as scored line 127.

Since all three contacts 100, 101 and 102 are the same, only contact 102 will be discussed in detail hereinv As in the case of the structure of FIG. 1 each of the contacts consists of two upright legs 120 and 106, with a transverse section 125 connecting said two upright legs 120 and 106 together.

Each of the upright legs has a supporting member thereon which extends down through the printed circuit board 114 to hold the contacts on the board. More specifically contact 102 has posts 122 and 113 which extend from legs 120 and 106, respectively, down through circuit board 114 and to which another connection can be made. such as a wire wrap connection or other suitable type connection.

It is to be noted that the two legs 122 and 113 are diagonally positioned. The two other diagonal corners of the contact 102 include legs 115 and 124, which extend from legs 106 and 120, respectively, and which mount upon the surface of printed circuit board 114.

The upright leg 120 is much the same as the upright leg 12 of FIG. 1 and will not be discussed in detail herein. However, one important difference is that the upright leg 120 of contact 102 of FIG. 3 has an embossed section 128 therein which adds to the structural strength of the leg.

The other upright leg 106, however, is quite different from the corresponding upright leg 13 of contact of FIG. 1. It will be seen that the upright leg 106 in FIG. 3 is essentially flat and the edges thereof are not bent backwards to add structural strength to the leg. Similarly, the portion 107 of leg 106, which extends inwardly and downwardly into the U of the contact, also does not have its edges bent backwards to provide structural strength. With the configuration of FIG. 3, i.e., with the flat configuration of leg 106 and its extension 107, the load imposed thereon when an edge of a printed circuit board is inserted therein is fairly evenly distributed over the upright portion 106 of the leg and the bent-over portion 107. as well as the portion 108 where the bending-over actually occurs. Because of this distributed load. the leg 106 and its bent-over portion 107 will tolerate more bending and stress than will the structure of FIG. 1, where more bending and stress is likely to occur, without producing permanent distortion therein, particularly at the bending-over section 108. F

To further protect the leg 106 of contact 102 of FIG. 3 there i is provided the anti-overstress clement 109 which extends backwardly towards the main upright leg 106 and which will come into contact therewith before the coefficient of elasticity of any portion of the leg element has been exceeded.

Other features of thestructure of FIG 3 include the embossment ll0,which is convex in nature and .extends outwardly. towards the opposing leg 120, and is a portion of leg 106 which makes electricaleontact with the edge of the circuit board inserted therein, ;Another embossed portion 111 functions to provide additional structural strength tothe leg 106 at the portion where the width of the leg hasbe'en diminished due to the cut-out section 130. .Suchcut-out section 130 is necessary to facilitate the bending back of section 112 of the edge of leg 106, and -to which section 112 the post 113 is connected, as can be seen from FIG. 3. Further, because of the bent-over portion 107, the bentback portions 1 l2 and 115 of leg 106 could be bent forwardinstead of backwards."

It is to be understood that the form of the invention shown and described herein is but a preferred embodiment thereofand that various modifications can be made in the details of design, such as proportion and cross-sectional configuration of the legs ofthe contacts, without departing from the spirit and scope of the invention. I a

What isclaimedis:

1. A free standing contact for mounting in a board and comprising:

a U-shaped portion having a first and second leg portions with surfaces facing each other, and a transverse portion joining together one end of each of said first and second leg portions;

the free end of said first leg portion being bent over and downwardly into the U-configuration and at an angle towards said second leg portion;

at least one edge of each of said second leg portion and the lower part of the edge of said first leg portion being bent back in a direction away from the facing surface of the opposite leg portion to form cross-sectional areas of said first and second leg portions into generally L-shaped configurations;

said bent-back edges extending beyond the said transverse portion to form securing elements for insertion into mating holes in said board to secure and position said contact on said board.

2. A free standing contact in accordance with claim 1 in which:

at least one edge of the bent over free end of said first leg portion is bent back and away from the major surface of said opposite leg to provide structural strength to said bent-over portion.

3. A free standing contact in accordance with claim 1 in which:

the tip of said bent-over portion of said first leg portion is bent back diagonally towards said major surface of said first leg portion.

4. A plurality of free standing contacts for mounting on a first board along a line to form an elongated slotlike opening for receiving the edge of a second board and for making a series of electrical contacts therewith, with each contact comprising:

with claim in which:

ond leg portion, and a transverse portion, with each of said first and second leg portions having major surfaces which face each other and which are substantially parallel with each other;

said first leg portion having its free end bent over and extending down into said U and diagonally towards said second leg portion;

sections of the edges of said first and second leg portions being bent away from the said facing major 10 surface'of said opposite leg to form said legs into elements with at least a portion of their crossseetional configuration being substantially U- shaped;

pair of said bent back edges which are diagonally positioned extending beyond said transverse portion and configured to mate with receiving apertures prepared therefor in said first board.

5. A plurality of free standing contacts in accordance in which said first board has a plurality of receiving apertures formed therein for receiving said plurality of free standing contacts; and

in which said contacts are spaced apart a distance equal to the receiving aperture spacing on said first circuit board.

6. A plurality of free standing contacts in accordance the tip of said bent-over portion of said first leg portion of each free standing contact is bent back diagonally towards said major surface of said first leg portion to limit the excursion of said bent-over portion towards said first leg.

7. A plurality of free standing contacts for mounting into mating holes in a first board along a line to form an elongated slot-like arrangement for receiving the edge of a second board and for making a series of electrical connections therewith, with each of said contacts comprising: i

a U-shaped portion having a first and second leg portions with surfaces facing each other, and a transverse portion joining together one of each of said first and second leg portions;

the free end of said first leg portion being bent over and downwardly into the U configuration and at an angle towards said second leg portion;

at least a section of one edge of each of said first and second leg portions being bent back in a direction away from the facing surface of the opposite leg portion to cause a section of the cross-sectional areas of said first and second leg portions to include an L-shaped configuration;

said bent-back edges extending beyond the said transverse portion to form post-like terminals for insertion into said mating holes in said first board; the tip of said bent-over portion of ,said leg portion of each free standing contact is bent back diagonally towards said major surface of said first leg portion to limit the excursion of said bent-over portion towards said first leg portion when the edge of said second board is inserted between said second leg portion and the bent-over portion of said first leg portion. 

1. A free standing contact for mounting in a board and comprising: a U-shaped portion having a first and second leg portions with surfaces facing each other, and a transverse portion joining together one end of each of said first and second leg portions; the free end of said first leg portion being bent over and downwardly into the U-configuration and at an angle towards said second leg portion; at least one edge of each of said second leg portion and the lower part of the edge of said first leg portion being bent back in a direction away from the facing surface of the opposite leg portion to form cross-sectional areas of said first and second leg portions into generally L-shaped configurations; said bent-back edges extending beyond the said transverse portion to form securing elements for insertion into mating holes in said board to secure and position said contact on said board.
 2. A free standing contact in accordance with claim 1 in which: at least one edge of the bent over free end of said first leg portion is bent back and away from the major surface of said opposite leg to provide structural strength to said bent-over portion.
 3. A free standing contact in accordance with claim 1 in which: the tip of said bent-over portion of said first leg portion is bent back diagonally towards said major surface of said first leg portion.
 4. A plurality of free standing contacts for mounting on a first board along a line to form an elongated slot-like opening for receiving the edge of a second board and for making a series of electrical contacts therewith, with each contact comprising: a U-shaped portion having a first leg portion, a second leg portion, and a transverse portion, with each of said first and second leg portions having major surfaces which face each other and which are substantially parallel with each other; said first leg portion having its free end bent over and extending down into said U and diagonally towards said second leg portion; sections of the edges of said first and second leg portions being bent away from the said facing major surface of said opposite leg to form said legs into elements with at least a portion of their cross-sectional configuration being substantially U-shaped; a pair of said bent back edges which are diagonally positioned extending beyond said transverse portion and configured to mate with receiving apertures prepared therefor in said first board.
 5. A plurality of free standing contacts in accordance with claim 4 which are formed from a single continuous strip of metal and which, during forming, are joined together by a carrier strip; in which said first board has a plurality of receiving apertures formed therein for receiving said plurality of free standing contacts; and in which said contacts are spaced apart a distance equal to the receiving aperture spacing on said first circuit board.
 6. A plurality of free standing contacts in accordance with claim 5 in which: the tip of said bent-over portion of said first leg portion of each free standing contact is bent back diagonally towards said major surface of said first leg portion to limit the excursion of said bent-over portion towards said first leg.
 7. A plurality of free standing contacts for mounting into mating holes in a first board along a line to form an elongated slot-like arrangement for receiving the edge of a second board and for making a series of electrical connections therewith, with each of said contacts comprising: a U-shaped portion having a first and second leg portions with surfaces facing each other, and a transverse portion joining together one of each of said first and second leg portions; the free end of said first leg portion being bent over and downwardly into the U configuration and at an angle towards said second leg portion; at least a section of one edge of each of said first and second leg portions being bent back in a direction away from the facing surface of the opposite leg portion to cause a section of The cross-sectional areas of said first and second leg portions to include an L-shaped configuration; said bent-back edges extending beyond the said transverse portion to form post-like terminals for insertion into said mating holes in said first board; the tip of said bent-over portion of said leg portion of each free standing contact is bent back diagonally towards said major surface of said first leg portion to limit the excursion of said bent-over portion towards said first leg portion when the edge of said second board is inserted between said second leg portion and the bent-over portion of said first leg portion. 